Sound translating device



0ct.5,-1943. H. c. PYE 2,331,044"

SOUND TRANSLATING DEVICE Original Filed Nov. 27, 1939 2 Sheets-Sheet l wy? I 6 l2 FIG 2 INVENTOR. HAROLD C. PYE

. ATTORNEYS Oct. 5, 1943. r H. c. PYE 2,331,044

SOUND TRANSLATING DEVICE Original Filed Nov. 2'7, 1959 2 Sheets-Sheet 2 Q i :5 Q 1/ a 2 03 qo 00 A .2 8 g :3 l I I OUTPUT DECIBLES INVENTOR HAROLD C. PYE

. BY m fddnfrm ATTORNEYS Farmed Oct. 5, 1943 2,331,044 SOUND TRANSLATING DEVICE Harold C. Pye, Oak Park, 111., assignor to Automatic Electric Laboratories, Inc., a corporation of Delaware Original application November 27, 1939, Serial No. 306,287. Divided and this application October 1, 1941, Serial No. 413,184

4 Claims.

The present invention relatesto sound translating devices and more particularly to telephone transmitters. The present application is a division of the copending application of Harold C. Pye, Serial No. 306,287, filed November 2'7, 1939 which has now matured into United States Patent No. 2,288,839, dated July '7, 1942.

A conventional telephone transmitter is responsive to sound waves of difierent frequencies disposed within the audible frequency range and including background sound waves having frequencies disposed within a first band in the audible range and signal sound waves having fre quencies disposed within a second hand in the audible range. Ordinarily, the background soundsor noises have frequencies disposed toward the lower end of the audible range; while the signal sounds have frequencies disposed toward the higher end of the audible range. Consequently, the telephone transmitter transmits sound energy corresponding both to the background noises and to the signal sounds; thereby to cause a telephone receiver associated with the telephone transmitter to reproduce both the background noises and the signal sounds.

Accordingly, it is-an object of the present invention to provide a telephone transmitter embodying an improved arrangement for prevent ing the transmitter from transmitting sound energy corresponding to the background noises.

Another object of the invention is to provide in a transmitter, an improved mechanical filter arrangement for filtering out undesirable noises having frequencies disposed within a predetermined frequency band in the audible frequency range of the transmitter.

Another object of the invention is to provide in a sound translating device having a predetermined-inherent acoustical response over a given frequency range, an improved mechanical filter arrangement for altering the efiective acoustical response of the device over a given frequency in the open end of the casing, first and second electrodes arranged in the casing, the first electrode being rigidly connected to the diaphragm and movable therewith and the second electrode being resiliently connected to the casing and movable with respect thereto, and a movable mechanical system coupled to the second electrode. During the operation of the transmitter the vibratory diaphragm is subjected to sound waves having different frequencies in the audible range including background sound waves having frequencies disposed in a first band in the audible range and signal sound waves to be transmitted having frequencies disposed in a second band in the audible range, whereby the sound energy transmitted by the transmitter corresponds to the relative movement between the electrodes,

the movable mechanical system constitutes means for filtering out the background sound energy. More particularly, the mechanical system comprises, mass and stiffness characteristics which are so proportioned and related that the second electrode is moved with the first electrode when the diaphragm is subjected to the sound waves having frequencies disposed in the first band in the audible range.

More particularly the transmitter comprises an impedance element in the form of a charge of carbon granules disposed between the first and second electrodes, whereby relative movement between the first and second electrodes is efiectlve to control the effective impedance of the impedance element such that the variation in effective impedance of the impedance element corresponds to sound energy to be transmitted by the transmitter.

Further it is noted that the transmitter has a predetermined inherent acoustical response over the audible frequency range and that the movable mechanical system constitutes a mechanical filter for establishing a cut-off point disposed within the audible range, whereby the effective acoustical response of the device is a substantially negligible value on one side of the cut-off point and an appreciable value on the other side of the cut-off point, wherein the location of the cut-off point within the audible range is deter-- mined by both the mass and stifiness charactercomprises a substantially cup-shaped casing, a

vibratory diaphragm, means for securing the diaphragm adjacent the peripheral edge thereof istics of the system. Finally, it is noted that the effective acoustical response of the transmitter is a substantially negligible value on the side of the cut-off point disposed toward the low frequency end of the audible range and an appreciable value on the side of the cut-off point disposed toward the high frequency end of the audible range, whereby the transmitter is efl'ective to transmit sound energy corresponding only to relatively high frequency signal sounds.

Further features of the invention pertain to the particular construction and arrangement of the elements of the sound translating device, whereby the above-outlined and additional operating features are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which Figure 1 is a plan view of a sound translating device embodying the present invention; Fig. 2 is a longitudinal sectional view of the device taken along the line 2-2 in Fig. l; and Fig. 3 is a graphic illustration of the performance characteristics of sound translating devices of the type illustrated in Figs. 1 and 2.

Referring now more particularly to Figs. 1 and 2 of the drawings, there is illustrated a sound translating device in the form of a telephone transmitter H) which comprises a substantially cup-shaped housing including a flat bottom wall I2, a central dome I3, a cylindrical side wall l4, an annular flange I5 and a cylindrical side wall IS, the flange |5 being disposed between the side walls I 4 and I6. Preferably, the housing II is formed of a suitable aluminum alloy in order to obtain a rigid lightweight mounting for the elements of the transmitter and supports a suitable mouthpiece, not shown. An annular face plate I1 is arranged Within the side wall l6 of the housing H and retained in place by an annular flange l8 spun' from the side wall I6 into engagement with the face plate l1. Preferably the face plate I1 is formed of a suitable aluminum alloy and is provided with a number of openings l9 therein arranged in a circular pattern in order to permit sound waves to enter the housing H. An annular groove 20 is provided in the cylindrical side wall of the face plate IT in order to provide a resilient gripping action between the side wall of the face plate l1 and the side wall l6 of the housing II when the annular flange I8 is spun from the side wall I 6 into engagement with the face plate H.

The housing l encloses a moving system comprising a composite diaphragm including a primary diaphragm 2|, a secondary diaphragm 22 and a casing element 23. The primary diaphragm 2| comprises a substantially central conical dome 24 and a wide annular flange 25. The annular flange 25 carried by the primary diaphragm 2| overlies the annular flange I5 carried by the housing II and is clamped between annular shoulders 26 and 21 respectively provided on the flange l5 and the face plate I1. Also a thin cushioning ring 28 formed of insulating material is disposed between the flange 25 carried by the primary diaphragm 2| and the annular shoulder 21 provided on the face plate I1. Finally the front wall of the primary diaphragm 2| is covered with a moisture-proof protective covering 29.

The casing element 23 comprises a substantially central dome 30 and a wide annular flange 3|. Finally the secondary diaphragm 22 comprises an annular ring disposed between the annular flange 25 carried by the primary diaphragm 2| and the annular flange 3| carried by the easing element 23; the inner periphery of the secondary diaphragm 22 being suitably secured to the annular flange 3| and the outer periphery of the secondary diaphragm 22 being suitably secured to the'annular flange 24. The center of the dome 24 carried by the primary diaphragm 2| is secured to the center of the dome 36 carried by the casing element 23 by an eyelet or rivet 32, thus forming a composite diaphragm assembly which is very stiff over the central conical portion and extremely flexible over the outer edge flange portion. Also it is noted that the eyelet 32 has an opening 33 provided therein in order to provide a breathing action between the interior of the casing element 23 and the outside atmosphere. Also, the telephone transmitter ||l comprises a casing element 34 including a substantially central dome 35 and a wide annular flange 36, the dome 35 carried by the casing element 34 being arranged within the dome |3 carried by the housing The casing element 34 is retained in position within the housing II by an annular corrugated flexible paper bellows 31 extending between and cemented to the bottom wall |2 carried by the housing H and the annular flange 36 carried by the casing element 34. Preferably, the primary diaphragm 2|, the secondary diaphragm 22 and the casing elements 23 and 34 are formed of thin duralumin sheet metal in order to obtain the combination of lightweight parts having high tensile strength.

A ring-shaped electrode 38 is suitably secured to the annular flange 3| carried by the casing element 23 adjacent the dome 30 thereof; similarly, a ring-shaped electrode 39 is suitably secured to the annular flange 36 carried by the casing element 34 adjacent the dome 35 thereof. Preferably, the electrodes 38 and 39 are formed of solid carbon and are sealed with respect to each other by an annular corrugated flexible paper bellows 40 extending therebetween and cemented thereto. Further it is noted that a charge of carbon granules, not shown, is arranged within the domes 30 and 35 of the casing elements 23 and 34, respectively, and extends between the electrodes 38 and 39, the interior surfaces of the domes 30 and 35 respectively carried by the casing elements 23 and 34 being varnished in order to electrically insulate the casing elements 22 and 34 from the charge of carbon granules disposed therein.

A mechanical low-pass fllter arrangement is commonly associated with the casing elements 23 and 34 which comprises three metallic rings 4|, 42 and 43 and two rings of insulating material 44 and 45. The metallic rings 4| and 43 are respectively secured to the annular flanges 3| and 36 respectively carried by the casing elements 23 and 34; while the insulating rings 44 and 45 are respectively secured between the metallic rings 4|, 42 and 42, 43, thereby to provide a bellows construction surrounding the electrodes 38 and 39 and extending between the annular flanges 3| and 36.

The bottom wall l2 of the housing carries an electrical terminal 46 electrically connected thereto and an electrical terminal 41 electrically insulated therefrom, the terminal 41 being electrically connected by a flexible conductor 48 to a plug 49 carried by the dome 35 of the casing element 34. Accordingly the terminal 46, the housing H, the primary diaphragm 2|, the casing element 23 and the electrode 38 are arranged in series circuit relation; while the terminal 41, the conductor 48, the plug 49, the casing element 34 and the electrode 39 are arranged in series circuit relation, the charge of carbon granules being disposed between the electrodes at and as.

between the electrodes 38 and 39 is variably compressed in accordance with the relative movements between the electrodes 38 and 39, thereby to vary the electrical impedance or resistance of the circuit extending between the terminals 46 and 41.

Also during operation of the telephone transmitter l0, movement of the primary diaphragm 2|, and consequently movement of the casing element 23, is damped by the action of a resonance chamber 50 formed between the primary diaphragm 2| and the face plate l1; movement of the casing element 34 is damped by the resilient bellows 31; whilemovement of the casing element 23 with respect to the casing element 34 is damped by the resilient bellows 40 and by the breathing action of the air passing through the opening 33 formed inthe eyelet 32 incident to movement of the casing elements 23 and 34 with respect to each other. I

Finally it is. noted that the movements of the casing elements 23 and 34 with respect to each other, and consequently the movements of the electrodes 38 and 39 with respect to each other, are controlled by the mechanical low-pass filter arrangement disposed between the annular flanges 3| and 36 respectively carried by the casing elements 23 and 34.

. More particularly, at low frequencies, the

. mechanical low-pass filter arrangement constitutes in effect a substantially rigid connection between the annular flanges 3| and 36 respectively carried by the casing elements 23 and 34, thereby to cause the movements of the casing element 23 to be transmitted directly to the casing element 34. Accordingly, at low frequencies, the electrodes 38 and 39 are not moved substantially with respect to each other. Hence the mechanical low-pass filter arrangement prevents low frequency sound energy from being transmitted from the telephone transmitter or filters out low frequency sound energy. On the other hand, at high frequencies, the mechanical lowpass filter arrangement constitutes in effect no connection between the annular flanges 3| and 36 respectively carried by the casing elements 23 and 34, thereby to cause the casing element 23 to move with respect to the casing element 34. Accordingly, at high frequencies, the electrodes 38 and 39 are moved substantially with respect to each other. Hence the mechanical low-pass filter arrangement does not prevent high frequency sound energy from being transmitted from the telephone transmitter or permits high frequency sound energy to pass.

From the above description of the mode of operation of the mechanical low-pass filter arrangement commonly associated with the casing elements 23 and 34 it will be understood that the telephone transmitter is effective to transmit at substantial magnitudes only sound energy having a frequency disposed above a given cutoff frequency.

Further it will be understood that the point of cut-off of the telephone transmitter I!) may be controlled by varying the mass of the metallic rings 4|, 42 and 43 and by varying the stiffness of the insulating rings 44 and 45. More particularly, by increasing the stiffness of the insulating rings 44 and 45 or by decreasing the mass of the metallic rings 4|, 42 and 43, the

point of cut-off of the telephone transmitter 10 may be shifted from a. given frequency band to a higher frequency band; on the other hand, by decreasing the stifiness of the insulating rings 44 and 45 or by increasing the mass of the metallic rings 4|, 42 and 43, the point of cut-off of the telephone transmitter l0 may be shifted from a given frequency band to a lower frequency.

band. Further it will be understood that any reasonable number of insulating rings and metallic rings may be provided in the telephone transmitter l0, and that the number of insulating rings and metallic rings provided will not alone control the point of cut-off of the telephone transmitter ID, as the. point of cut-off of the telephone transmitter will be determined by the ratio between the composite mass of. the metallic rings and the composite stiifness of the insulating rings.

Referring now to Fig. 3, there is illustrated graphically two performance curves A and B of two telephone transmitters A and B having the general construction of the telephone transmitter I. It is noted that the telephone transmitter A has a cut-off point occurring between 300 and 400 cycles per second; thereby to cause the telephone transmitter A to transmit a current variation corresponding to a low sound output of the order of minus 8 decibels or below in the frequency band below 300 cycles per second, and to transmit a current variation corresponding to a high sound output of the order of plus 8 decibels or abovev in the frequency band above 400 cycles per second.

On the other hand, the telephone transmitter B has a cut-off point occurring between 700 and 300 cycles per second; thereby to-cause the telephone transmitter B to transmit a current variation corresponding to a low sound output of the order of 0 decibels or below in the frequency band below 700 cycles per second, and to transmit a current variation corresponding to a high sound output of the order of plus 7 decibels or above in the frequency band above 800 cycles per second.

A telephone transmitter of the general construction of the telephone transmitter I0 and having a performance curve corresponding to the performance curve A may be altered to have a performance curve corresponding to the performance curve B by appropriately increasing the stiffness of the insulating rings or by appropriately decreasing the mass in the manner previously explained.

While one embodiment of the invention has jacent the peripheral edge thereof in the open end or said casing, first and second electrodes arranged ln said casing, said first electrode being rigidly connected to said diaphragm and therewith, said second electrode being resiliently connected to said casing and movable with respect thereto, a movable mechanical system arranged in said casing and including a plurality of spacedapart mass rings and a plurality of interposed stiffness rings connected together to form a compact hollow cylindrical bellows-like structure extending between and coupled to said first and second electrodes, whereby the relative movement between said first and second electrodes is controlled, an' impedance element,'and means gov- 0f the metallic ings,

movable emed in accordance with the relative movement between said first and second electrodes for controlling the effective impedance of said impedance element, whereby the variation in the efi'ective impedance of said impedance element corresponds to sound energy to b transmitted.

2. A telephone transmitter comprising a substantially cup-shaped casing, a vibratory diaphragm, means for securing said diaphragm adjacent the peripheral edge thereof in the open end of said casing, first and second supports arranged in said casing, first and second electrodes respectively carried by said first and second supports and arranged in spaced-apart facing relationship, said first support being rigidly connected to said diaphragm and movable therewith, said second support being resiliently connected to said casing and movable with respect thereto, a movable mechanical system including a plurality of spaced-apart mass rings and a plurality of interposed stiffness rings connected together to form a compact hollow cylindrical bellows-like structure surrounding said electrodes and extend.- ing between and coupled to said supports, whereby the relative movement between said first and second electrodes is controlled, an impedance element disposed between said electrodes, and means governed in accordance with the relative movement between said first and second electrodes for controlling the efiective impedance of said impedanc element, whereby the variation in the effective impedance of said impedance element corresponds to sound energy to be transmitted.

3. A transmitter comprising first and second movable electrodes, means including a. vibratory member for controlling the movement of said first electrode, means including a movable mechanical system comprising a plurality of spaced-apart mass rings and a plurality of interposed stiffness rings connected together to form a compact hollow cylindrical bellows-like structure extending between and mechanically coupled to said first and second electrodes for controlling the movement of said second electrode, an impedance element, and means governed in accordance with the relative movement between said first and second electrodes for controlling the eflective impedance of said impedance element.

4. In a telephone transmitter comprising a vibratory diaphragm adapted to be subjected to sound waves having different frequencies in the audible range during operation thereof including background sound waves having low frequencies and sound waves to be transmitted having high frequencies, a first movable electrode mechanically connected to said diaphragm, whereby the movement of said first electrode is controlled by said diaphragm, a second movable electrode associated with said first electrode, whereby the sound energy transmitted by said transmitter corresponds to the relative movement between said electrodes, and means including a movable mechanical system commonly mechanically coupled to said first and second electrodes for controlling the movement of said second electrode, the mass and stiffness of said mechanical system being so proportioned and related that said second electrode is moved with said first electrode when said diaphragm is subjected to sound waves having low frequencies disposed in said audible range, whereby the background sound energy is filtered out.

HAROLD C. PYE. 

